/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | foam-extend: Open Source CFD
   \\    /   O peration     | Version:     4.1
    \\  /    A nd           | Web:         http://www.foam-extend.org
     \\/     M anipulation  | For copyright notice see file Copyright
-------------------------------------------------------------------------------
License
	This file is part of foam-extend.

	foam-extend is free software: you can redistribute it and/or modify it
	under the terms of the GNU General Public License as published by the
	Free Software Foundation, either version 3 of the License, or (at your
	option) any later version.

	foam-extend is distributed in the hope that it will be useful, but
	WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with foam-extend.  If not, see <http://www.gnu.org/licenses/>.

Description
	Gauss-Seidel solver for symmetric and asymmetric matrices.  In
	order to improve efficiency, the residual is evaluated after every
	nSweeps sweeps.

\*---------------------------------------------------------------------------*/

#include "BlockGaussSeidelSolver.H"

// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

// Construct from matrix and solver data stream
template<class Type>
Foam::BlockGaussSeidelSolver<Type>::BlockGaussSeidelSolver
(
	const word& fieldName,
	const BlockLduMatrix<Type>& matrix,
	const dictionary& dict
)
:
	BlockIterativeSolver<Type>
	(
		fieldName,
		matrix,
		dict
	),
	gs_(matrix),
	nSweeps_(readLabel(this->dict().lookup("nSweeps")))
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

template<class Type>
typename Foam::BlockSolverPerformance<Type>
Foam::BlockGaussSeidelSolver<Type>::solve
(
	Field<Type>& x,
	const Field<Type>& b
)
{
	// Create local references to avoid the spread this-> ugliness
	const BlockLduMatrix<Type>& matrix = this->matrix_;

	// Prepare solver performance
	BlockSolverPerformance<Type> solverPerf
	(
		typeName,
		this->fieldName()
	);

	Type norm = this->normFactor(x, b);

	Field<Type> wA(x.size());

	// Calculate residual.  Note: sign of residual swapped for efficiency
	matrix.Amul(wA, x);
	wA -= b;

	solverPerf.initialResidual() = cmptDivide(gSum(cmptMag(wA)),norm);
	solverPerf.finalResidual() = solverPerf.initialResidual();

	// Check convergence, solve if not converged

	if (!this->stop(solverPerf))
	{
		// Iteration loop

		do
		{
			for (label i = 0; i < nSweeps_; i++)
			{
				gs_.precondition(x, b);

				solverPerf.nIterations()++;
			}

			// Re-calculate residual.  Note: sign of residual swapped
			// for efficiency
			matrix.Amul(wA, x);
			wA -= b;

			solverPerf.finalResidual() = cmptDivide(gSum(cmptMag(wA)), norm);
		} while (!this->stop(solverPerf));
	}

	return solverPerf;
}


// ************************************************************************* //
